a, Interindividual (pink, n = 18 individuals) and intraindividual (blue, n = 6 years) variation distributions, calculated using coefficient of variation per cell subset. Boxes represent 25th and 75th percentiles around the median (line). Whiskers, 1.5× interquantile, range. b, Percentage of total variance per cell subset explained by interindividual variation (total sum of squares attributed to subject) and intraindividual, variation (residual sum of squares). c, Lengths of within-individual trajectories in young adults versus older adults as measured in the PCA twodimensional, space (P = 0.03, two-tailed t-test, n = 3 young adults and n = 15 older adults). Boxes represent 25th and 75th percentiles around the median, (line). Whiskers, 1.5× interquantile range. d, Spearman correlations of individual-level slopes of cell subsets highly correlated with the first two principal, components with age and the individual’s baseline position along the PCA two-dimensional axes (right and left boxplots, respectively, P = 1.7 × 10–4, twotailed, paired t-test, n = 39). Boxes represent 25th and 75th percentiles around the median (line). Whiskers, 1.5× interquantile range. *P < 0.05, ***P = 0.001.